1. Technical Field
The present invention relates to a liquid ejecting apparatus, a drive circuit, and a head unit.
2. Related Art
An apparatus which uses a piezoelectric element (for example, a piezo element) is known as an ink jet printer which prints an image or a document by ejecting ink. Piezoelectric elements are provided in correspondence with each of multiple nozzles in a head unit, each of the piezoelectric elements is driven in accordance with a drive signal, and thus, a predetermined amount of ink (liquid) is ejected from the nozzle at a predetermined timing to form dots. The piezoelectric element is a capacitive element such as a capacitor from a viewpoint of electricity, and needs to receive a sufficient current in order to operate the piezoelectric elements of each nozzle.
For this reason, an original drive signal is amplified by an amplification circuit, is supplied to a head unit as a drive signal, and drives the piezoelectric elements. It is recommended that an amplification circuit uses a method (linear amplification, refer to JP-A-2009-190287) of current-amplifying the original drive signal in an AB class or the like. However, since power consumption increases and energy efficiency decreases in the linear amplification, a D-class amplification is also proposed in recent years (refer to JP-A-2010-114711). In short, in the D-class amplification, a pulse width modulation or a pulse density modulation of an input signal is performed, a pair of transistors which is configured by a high side transistor and a low side transistor that are inserted in series between power supply voltages is switched in accordance with the modulated signal, an output signal which is generated by the switching is filtered by a low pass filter, and thus, the input signal is amplified.
However, in the D-class amplification method, energy efficiency increases compared to a linear amplification method, but if a piezoelectric element is driven in a wide voltage range, a power supply voltage of a pair of transistors increases. For this reason, there is room for improvement in terms of reducing power consumption.